2020 Volume 55 Issue 11 Pages 703-714
The time-averaged airflow around a mileage competition vehicle was analyzed using computational fluid dynamics in order to optimize the body design to reduce aerodynamic drag and achieve lower fuel consumption. The design parameters were the minimum ground clearance h, the radial clearance of the wheels Sr, and the axial clearance of the wheels Sz. The speeds of the inlet airflow and the ground, relative to the vehicle at rest in the computational domain, were both set to 30 km/h based on the running conditions in the mileage competition. The rotation speed of the wheels was also included in the simulation. The drag exhibits a sharp minimum for a particular minimum ground clearance, hmin, where a remarkable pressure recovery and a decay in the vorticity behind the vehicle body are found. Having optimized the Sr value to achieve a lower drag, the Sz value was then adjusted to keep the steering range of the front wheels. Finally, the pressure drag and friction drag per unit span at the spanwise center were calculated. The pressure drag on the rear body is also found to be minimized at hmin. The validity of the friction drag for the vehicle was confirmed by approximate calculations based on theoretical equations for a turbulent boundary layer above a flat plate.
